Even though System Profiler reports the ram as ok, it might not be. The only way to truly test it is to use a third party diagnostic. Apple techs have a bootable ASD disc they use. I test all my new ram with memtest on a 3-5 hour cycle. I did help a buddy trouble shoot a similar problem. He found it was a external drive giving him intermediate freezes. I believe Techtool Pro has a bootable disc that can test all available ram._________________MacMini 2.0GHz C2D (2009)
MacMini 2.16GHz Intel Core Duo
Dell Mini 10v *OSX 10.6.4*

Dino poke around the net for MemTest 4.2 or 4.21. If you can't find it I'll send you a copy when I get home later. What other diagnostic disk do you have at your disposal?_________________MacMini 2.0GHz C2D (2009)
MacMini 2.16GHz Intel Core Duo
Dell Mini 10v *OSX 10.6.4*

I can mail you 1 gb ram sticks. you can pull the pair of 2's that came with it and put in the four 1gb sticks. Let me know if you need them. Dirt cheap. They are pulls from 2 new macmini's less then 1 day use on all 4 of them. They run around 30 each new. I would sell them to you. Less then half price ( with shipping free) if you want them pm me. If it does not work you can send them back. phil_________________2010 Mm 2.4 C2D oem 320gb hdd 8gb ram
2012Mm base 2.5 with 16gb ram diy fusion drive
2012Mm quad with 8gb ram oem 1tb hdd

sounds like hard drive corruption or a program bug in 10.6.3 I have the same iMac with the 3.06 processor which is your cpu. the only difference is I purchased the 4850 video card update. My imac is booting._________________2010 Mm 2.4 C2D oem 320gb hdd 8gb ram
2012Mm base 2.5 with 16gb ram diy fusion drive
2012Mm quad with 8gb ram oem 1tb hdd

OK. That's what I thought. The Update! I'm going to reinstall the 10.6.3 Combo Update from Apple's web site. Is the Combo one the one to Install or just the regular one. The Combo has like 50 more MB's. It should not hurt to install again. I did the normal Software Update when I installed it 3 days ago. I'm going to try that before I do a complete Erase & Install, as I'm not too excited about doing that. Phil, Thanks for the Ram offer anyway!_________________iMac 27" 3.06 8GB ATI 4670 1TB HD
Mac Mini 1.83 Intel Core 2 Duo 4GB 80 GB
Macbook Pro 2.4 GHz i5 8 GB Ram 500 GB HD
Power Mac G5 1.8 GHz
Apple TV 3rd Gen
Time Capsule 1st Gen 2TB

I've been having random freezes for most of the last week. They are really weird in that I know the iMac has crashed but I can still use the mouse and can even connect to it remotely and browse around the HDD. When it froze this morning I was watching the Space Shuttle launch and even though the machine had frozen the media kept playing. the mouse was moving around the screens but I couldn't operate any menu's or close any apps. I finished watching the launch before doing a hard reset to restart the machine.

Looking through my console logs it turned out to be related to my printer, which I haven't used in the last week. the logs showed the driver having crashed around the time my system froze.

I know this isn't likely to be your issue but I'm guessing my printer driver problem has been triggered by the OS update to 10.6.3

On your system Dino, have you disturbed the iMac at all ? I've had similar issues before in my PC days with video card not being seated properly in the PCI / AGP slots, also ram needing reseating.

Also on a PC you normally get BIOS beeps on startup which can help to narrow down a problem. The beeps sound at different rates for each fault. Like a sort of morse code. I'm not sure if the Mac can be set to do something similar.

Cypher, It's been a while since I shut down or restarted. Probably a Week at least. Funny you should mention Printer Driver. I have to use the OSX Gutenprint Driver for my Printer. It's an old HPPSC750 Multi Function. But the Gutenprint Driver is just to Print. So I also installed the HP Mac OSX Drivers from their Website in order to use the Scanner. So that could be my Problem as well. Who knows?_________________iMac 27" 3.06 8GB ATI 4670 1TB HD
Mac Mini 1.83 Intel Core 2 Duo 4GB 80 GB
Macbook Pro 2.4 GHz i5 8 GB Ram 500 GB HD
Power Mac G5 1.8 GHz
Apple TV 3rd Gen
Time Capsule 1st Gen 2TB